iOS document directories. Might use these on other platforms as well.

(cherry picked from commit 0238d15)

src/filesystem.cpp

@@ -52,6 +52,15 @@
 #include <algorithm>
 #include <set>
 
+// Copied from boost::predef, as it's there only since 1.55.
+#if defined(__APPLE__) && defined(__MACH__) && defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__)
+
+#define WESNOTH_BOOST_OS_IOS (__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__*1000)
+#include <SDL_filesystem.h>
+
+#endif
+
+
 static lg::log_domain log_filesystem("filesystem");
 #define DBG_FS LOG_STREAM(debug, log_filesystem)
 #define LOG_FS LOG_STREAM(info, log_filesystem)
@@ -617,6 +626,14 @@ void set_user_data_dir(std::string newprefdir)
 
 	std::string backupprefdir = ".wesnoth" + get_version_path_suffix();
 
+#ifdef WESNOTH_BOOST_OS_IOS
+	char *sdl_pref_path = SDL_GetPrefPath("wesnoth.org", "iWesnoth");
+	if(sdl_pref_path) {
+		backupprefdir = std::string(sdl_pref_path) + backupprefdir;
+		SDL_free(sdl_pref_path);
+	}
+#endif
+
 #ifdef _X11
 	const char* home_str = getenv("HOME");